This invention relates to a process for enriching certain isomers in an olefin stream.
Many industrial processes produce olefin streams that are mixtures of olefins. Olefins are frequently used in the manufacture of polymers such as polyethylene, as drilling mud additives, or as intermediates for the production of oil additives and detergents. Some industrial processes manufacture olefins streams by oligomerizing ethylene over an alpha olefin catalyst to produce mixtures of olefins having a broad range of carbon numbers. In some applications it will be desirable to obtain olefins enriched in certain isomers for enhanced properties depending on the applications,
U.S. Pat. No. 4,946,560 described a process for the separation of internal olefins from alpha olefins by carrying out a Diels-Alder reaction by contacting a feedstock with an adducting compound such as anthracene to form an olefin adduct (Diels-Alder adduct), separating the adduct from the feedstock, dissociating the olefin adduct through heat to produce anthracene and an olefin composition enriched in alpha olefin, and separating out the anthracene from the alpha olefin.
U.S. Pat. No. 6,184,431 describes a process for the separation of alpha and internal olefins from saturated compounds by contacting a feedstock with a linear polyaromatic compound to form a reaction mixture, comprising linear polyaromatic compound-olefin adducts and saturated hydrocarbons, separating the adducts from the saturated hydrocarbons, then dissociating the linear polyaromatic compound-olefin adducts to form linear polyaromatic compounds and an olefin composition.
U.S. Pat. No. 6,271,434 describes a process for the separation of linear alpha olefins from a crude stream containing saturated hydrocarbons, internal olefins, branched olefins, and linear alpha olefins by contacting the feedstock with linear polyaromatic compound to form a reaction mixture comprising linear polyaromatic compound-olefin adducts, separating the adducts from the saturated hydrocarbons and dissociating the adducts to form linear polyaromatic compounds and olefin.
However, it is desirable to obtain a process with economical means to further enrich the desired olefin products.
There is provided a process for producing an olefin product enriched in trans-isomers from a mixed olefin feedstock comprising cis-isomer olefins and trans-isomer olefins comprising the steps of:
a) contacting the mixed olefin feedstock with a linear polyaromatic compound under conditions effective to form a reaction mixture comprising linear polyaromatic compound-olefin adducts;
b) separating the linear polyaromatic compound-olefin adducts from the unreacted olefins in the reaction mixture to form an adduct stream and an unreacted olefin stream;
c) dissociating the linear polyaromatic compound-olefin adducts in the adduct stream to form linear polyaromatic compounds and an olefin composition enriched in trans-isomer from the mixed olefin feedstock;
d) separating the linear polyaromatic compound formed in step c) from the olefin composition.
Further there is provided a process for producing an olefin product enriched in cis-isomers from a mixed olefin feed stock comprising cis-isomer olefins and trans-isomer olefins comprising the steps of:
a) contacting the mixed olefin feedstock with a linear polyaromatic compound under conditions effective to form a reaction mixture comprising linear polyaromatic compound-olefin adducts;
b) separating the linear polyaromatic compound-olefin adducts from the unreacted olefins in the reaction mixture to form an adduct stream and an unreacted olefin stream enriched in cis-isomers from the mixed olefin feedstock;
c) optionally recovering the olefins from the unreacted olefin stream.